CN109219521B

CN109219521B - Ink jet recording apparatus

Info

Publication number: CN109219521B
Application number: CN201780033829.3A
Authority: CN
Inventors: 时松宏行
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2016-06-03
Filing date: 2017-05-12
Publication date: 2020-08-04
Anticipated expiration: 2037-05-12
Also published as: EP3466698A1; WO2017208776A1; EP3466698A4; CN109219521A; US20190143709A1; JPWO2017208776A1; EP3466698B1; US10786998B2; JP6911844B2

Abstract

The invention provides an ink jet recording apparatus capable of discharging bubbles in an ink flow path more easily and reliably. An inkjet recording apparatus includes: an inkjet head (24) having a nozzle; an ink supply unit that supplies ink to the inkjet head; a driving unit that performs a driving operation for generating pressure fluctuation in ink; and a control unit, the ink jet head including: a common ink chamber (245) through which the supplied ink flows; a filter (246) provided in the common ink chamber; an individual flow path (2471) for feeding the ink passed through the filter to each nozzle; and an outlet (242) for discharging the ink in the common ink chamber, wherein the control unit supplies the ink at a pressure at which the ink leaks from the nozzle through the ink supply unit and discharges the ink from the outlet, while performing a predetermined driving operation by the driving unit, when performing a bubble discharge operation of the ink.

Description

Ink jet recording apparatus

Technical Field

The present invention relates to an inkjet recording apparatus.

Background

There is an inkjet recording apparatus that records an image on a recording medium by causing ink to be discharged from nozzles and land on the recording medium. In an inkjet recording apparatus, since a poor discharge of ink from nozzles causes deterioration of a recorded image, there are various techniques of inspecting whether or not the ink is discharged in an appropriate state and performing a maintenance operation based on the inspection result.

The cause of the defective discharge of ink from the nozzle is, for example, the mixing of foreign substances and air bubbles into the ink. In order to prevent the inclusion from mixing, conventionally, an ink jet recording apparatus is provided with a filter in the middle of an ink flow path from an ink tank to each nozzle. In addition, for the purpose of discharging bubbles, etc., a technique is known in which ink in a common flow path, in which ink is branched in individual flow paths communicating with a plurality of nozzles, is circulated and returned to an ink tank. In this case, there is a technique of making the ink pressure in the nozzle a negative pressure so that the ink is less likely to leak, and performing a driving operation to generate a micro-vibration of the ink level to such an extent that the ink is not discharged from the nozzle, and then circulating the ink, thereby easily peeling the air bubbles in the individual flow path and the nozzle from the wall surface and removing the air bubbles and foreign substances (for example, patent document 1).

Patent document 1 Japanese patent laid-open No. 2015-071231

However, when discharging bubbles in the ink flow path, it is difficult to return bubbles once entering the fine individual flow path and in the nozzle to the upstream side and discharge them, and there is a problem that it takes time and labor.

Disclosure of Invention

The invention aims to provide an ink jet recording apparatus capable of discharging bubbles in an ink flow path more easily and reliably.

In order to achieve the above object, the invention according to claim 1 is an inkjet recording apparatus including:

an inkjet head provided with a nozzle that discharges ink;

an ink supply unit configured to supply ink to the inkjet head;

a driving unit that performs a driving operation for generating the pressure fluctuation of the ink discharged from the nozzles; and

a control unit for controlling the operations of the ink supply unit and the drive unit,

the ink jet head includes:

a common flow path through which the ink supplied to the inkjet head flows;

a filter provided in the common flow path and configured to pass the supplied ink therethrough;

an individual flow path for feeding the ink passed through the filter from the common flow path to the nozzles, respectively; and

a first discharge port for discharging the ink in the common flow path through the filter,

when performing the bubble discharge operation of the ink in the inkjet head, the control unit supplies the ink by the ink supply unit at a pressure at which the ink leaks from the nozzle and discharges the ink from the first discharge port while performing a predetermined driving operation by the driving unit.

In addition to the inkjet recording apparatus according to claim 1, the invention according to claim 2 is characterized by comprising:

an ink storage unit that stores the ink supplied to the common flow path; and

and a circulation flow path for returning the ink discharged from the first discharge port to the ink storage unit.

The invention according to claim 3 is the ink jet recording apparatus according to claim 1 or 2, wherein,

a first discharge valve for switching whether or not to discharge the liquid from the first discharge port,

the controller closes the first discharge valve in a case where a normal discharge operation for recording an image is performed, and opens the first discharge valve in a case where the bubble discharge operation is performed.

The invention according to claim 4 is the inkjet recording apparatus according to any one of claims 1 to 3, wherein,

a second discharge port for discharging ink in the common flow path that does not pass through the filter,

the control unit discharges the supplied ink at least from the first discharge port when the bubble discharge operation is performed.

The invention according to claim 5 is, in addition to the inkjet recording apparatus according to claim 4, characterized in that,

a second discharge valve for switching whether or not to discharge the liquid from the second discharge port,

the control unit closes the second discharge valve at least in a case of a normal discharge operation for recording an image.

The invention according to claim 6 is the inkjet recording apparatus according to any one of claims 1 to 5, wherein,

in the case of performing the bubble discharge operation, the control unit causes the drive unit to perform a minute drive operation in which the pressure at which the ink is discharged from the nozzle is not varied during an image recording operation.

According to the present invention, the ink jet recording apparatus has an effect that bubbles in the ink flow path can be more easily and reliably discharged.

Drawings

Fig. 1 is a schematic diagram showing the structure of an inkjet recording apparatus.

Fig. 2 is a diagram illustrating a configuration relating to the flow of ink in the inkjet recording apparatus.

Fig. 3 is a cross-sectional view of an ink flow path in the inkjet head viewed from the front side.

Fig. 4 is a block diagram showing a functional configuration of the inkjet recording apparatus.

Fig. 5 is a flowchart showing a control procedure of the bubble discharge process.

Fig. 6A is a diagram showing a modification of the inkjet recording apparatus.

Fig. 6B is a diagram showing a modification of the inkjet recording apparatus.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic diagram showing a configuration of an inkjet recording apparatus 100 according to an embodiment of the present invention.

Fig. 1 shows a front view of the inkjet recording apparatus 100.

The inkjet recording apparatus 100 is a one-pass printer that includes a line head and forms a color image by discharging four-color inks at appropriate timings while moving a recording medium relative to the line head.

The inkjet recording apparatus 100 includes: a medium supply unit 10, a medium discharge unit 15, an image forming main body unit 20, an ink supply unit 30 (see fig. 2), a control unit 40 (see fig. 4), and the like. In the inkjet recording apparatus 100, the recording medium P stored in the medium supply unit 10 is conveyed to the image forming main body unit 20 under the control of the control unit 40, and after an image is formed, the recording medium P is discharged to the medium discharge unit 15.

The medium supply unit 10 conveys the recording media P stored therein to the image forming main body 20 one by one.

As the recording medium P, various media that can be carried on the outer circumferential surface of the image forming drum 281 while being curved, such as elements, films, and fabrics, may be used in addition to printing paper of various thicknesses.

The medium supply unit 10 includes: a paper feed tray 11 storing a recording medium P; and a sheet feeding plate 12 for feeding the recording medium P from the sheet feeding tray 11 to the image forming main body 20. The paper feed tray 11 is a plate-like member that can be placed on one or more recording media P. The paper feed tray 11 is provided to move up and down according to the amount of the recording medium P placed on the paper feed tray 11, and the uppermost recording medium P is held at a position conveyed by the paper feed plate 12 with respect to the direction of the upward and downward movement.

The sheet feeding plate 12 includes: a conveying mechanism that conveys the recording medium P on an endless belt 123 carried on the inside by a plurality of (e.g., two)

rollers

121 and 122 by driving the belt 123; or a feeding section that delivers the uppermost recording medium P placed on the paper feed tray 11 to the belt 123. The sheet feeding plate 12 conveys the recording medium P delivered from the feeding section to the belt 123 along the belt 123.

The image forming main body 20 includes: a delivery unit 27, an image forming drum 281, a head unit 282, an irradiation unit 283, a paper ejection unit 29, and the like.

The delivery unit 27 delivers the recording medium P delivered from the medium supply unit 10 to the image forming drum 281. The passing unit 27 includes: a swing arm 271 for supporting one end of the recording medium P conveyed by the sheet feeding plate 12; and a cylindrical delivery drum 272 for delivering the recording medium P carried by the swing arm portion 271 to the image forming drum 281, and the recording medium P on the paper feed plate 12 is lifted by the swing arm portion 271 and delivered to the delivery drum 272, whereby the recording medium P is guided in a direction along the outer peripheral surface of the image forming drum 281 and delivered to the image forming drum 281.

The image forming drum 281 has a cylindrical outer shape, and carries three recording media P at maximum on the outer peripheral surface of the cylindrical portion, and performs a conveying operation of conveying the recording media P in accordance with a rotating operation with respect to the central axis of the cylinder. A drum heater 2811 that heats the outer peripheral surface of the image forming drum 281 and the recording medium P is provided in the vicinity of the outer peripheral surface. Here, the drum heater 2811 is provided between a delivery position where the recording medium P is delivered toward the image forming drum 281 by the delivery unit 27 and an image recording position for the recording medium P by the head unit 282 in the rotational direction of the image forming drum 281. The heating operation time and intensity by the drum heater 2811 are controlled so that the recording medium P carried is at an appropriate temperature, based on the temperature measured on the outer peripheral surface of the image forming drum 281 by a temperature measuring unit, not shown. This ensures a proper curing speed or the like to the recording medium P when the ink lands on the recording medium P, thereby stably forming a high-quality image. The drum heater 2811 is, for example, an infrared heater or an electric heating wire that generates heat by energization. The drum heater 2811 may be provided inside the image forming drum 281 and may heat the outer circumferential surface by heat conduction.

The head unit 282 forms an image by discharging droplets of ink from a plurality of nozzle openings provided in a surface (nozzle surface) of the head unit 282 facing a surface (nozzle surface) of the recording medium P to be recorded of the recording medium P, at an appropriate timing with respect to the surface of the recording medium P to be recorded, which moves in accordance with rotation of the image forming drum 281, and landing the droplets on the surface of the recording medium P to be recorded. The head unit 282 includes one or more inkjet heads 24 (see fig. 2) provided with a plurality of nozzles. In the ink jet recording apparatus 100 of the present embodiment, a plurality of head units 282 are arranged at predetermined intervals in the transport direction of the recording medium P, and here, four head units are arranged corresponding to the respective four inks. The four head units 282 output inks of C (cyan), M (magenta), Y (yellow), and K (black), respectively. Here, the ink is a material that is cured by irradiation with ultraviolet rays. The ink is heated by an ink heater 2822 (see fig. 4) to a suitable temperature inside and/or outside the head unit 282.

Here, the head units 282 each include a plurality of nozzle opening portions arranged over an image forming width of the recording medium P in a width direction perpendicular to a conveyance direction of the recording medium P conveyed on the image forming drum 281 and a line head capable of forming an image by one pass by discharging ink from the nozzle opening portions to the recording medium P while moving the recording medium P in the conveyance direction. The head unit 282 is attached to a support portion (carriage), not shown, and a motor and a brake for position adjustment are operated by the unit position adjustment drive portion 58, so that the relative position between the head unit 282 and the image forming drum 281, particularly the distance from the outer peripheral surface from the image forming drum 281, can be changed.

Here, the irradiation unit 283 irradiates energy rays (electromagnetic waves) of a predetermined wavelength and ultraviolet rays in a near ultraviolet region (wavelength of about 400 nm) and cures and fixes ink discharged from the head unit 282 and landed on the recording medium P (i.e., an image formed by the ink). the irradiation unit 283 has, for example, a light emitting diode (L ED) that generates ultraviolet rays, and irradiates the recording medium P with ultraviolet rays by applying a voltage to the L ED and flowing a current by a driving operation of the irradiation driving unit 51 (see fig. 4). the irradiation unit 283 is provided so that ultraviolet rays can be irradiated on the recording medium P after the discharge of ink from the head unit 282 is completed on the recording medium P conveyed by the rotation of the image forming drum 281 and at a position before the recording medium P is transferred to the paper discharge unit 29, and a shield plate 283a is provided so as to cover L ED and a set range in order to reduce the amount of ultraviolet rays leaking outside the set range in which the recording medium P is irradiated with ultraviolet rays.

Further, the structure of the irradiation unit 283 to generate ultraviolet rays is not limited to L ED. and the irradiation unit 283 may be provided with, for example, a mercury lamp, and when the ink has a property of being cured by receiving an energy ray other than ultraviolet rays, a known light source to generate an energy ray of a wavelength for curing the ink is provided instead of the structure to generate ultraviolet rays.

The recording medium P on which the ink that has landed by the paper discharge unit 29 after completion of image formation is solidified is conveyed to the medium discharge unit 15. The paper discharge unit 29 includes a cylindrical delivery roller 291, a plurality of (e.g., two)

rollers

292 and 293, an annular belt 294 supported on the inner surface by the

rollers

292 and 293, and the like. The delivery roller 291 receives the recording medium P from the image forming drum 281 and guides the recording medium P on the belt 294. The paper discharge unit 29 conveys and feeds the recording medium P delivered from the delivery roller 291 to the belt 294 to the medium discharge unit 15 by moving the recording medium P along with the belt 294 that moves around with the rotation of the

rollers

292 and 293.

The medium discharge unit 15 stores the recording medium P fed out from the image forming main body 20 by the paper discharge unit 29 until the user takes out the recording medium P. The medium discharge unit 15 includes a plate-shaped paper discharge tray 16 and the like, and the recording medium P after image formation is placed on the paper discharge tray 16.

The control unit 40 controls operations of the medium supply unit 10, the image forming main body unit 20, the ink supply unit 30, and the medium discharge unit 15, and forms an image on the recording medium P in accordance with data of an image to be formed based on an image forming command (job) and settings related to image formation.

The conveyance unit is constituted by the medium supply unit 10, the image forming drum 281 of the image forming main body 20, the delivery unit 27, the sheet discharge unit 29, and the medium discharge unit 15.

The ink supply unit 30 stores inks of respective colors used for recording images and supplies the inks to the inkjet head 24. Here, each configuration of the ink supply unit 30 is disposed on a dedicated rack or the like, and is connected to the image forming main body 20 via a pipe or the like.

Next, a description will be given of a configuration relating to the flow of ink from the ink supply unit 30 to the image forming main body unit 20 of the inkjet recording apparatus 100 of the present embodiment.

Fig. 2 is a diagram illustrating a configuration relating to the flow of ink in the inkjet recording apparatus 100 according to the present embodiment.

The ink supply unit 30 includes a main tank 31, a filter 311, a supply pump 32, a supply valve 33, and the like.

The ink in the main tank 31 is transferred to the first subtank 21 of the image forming main body portion 20 through the supply valve 33 by the operation of the supply pump 32. The filter 311 prevents foreign matter such as dust and dirt, foreign substances, and the like from being mixed into the main tank 31 opened to the atmosphere. The supply valve 33 determines whether or not ink can be supplied from the main tank 31 to the first sub tank 21. The supply valve 33 is an electromagnetic valve that is opened and closed based on the control operation of the control unit 40, but may be manually switched between opening and closing when the main tank 31 is replenished with ink and when the main tank 31 is exchanged. The supply valve 33 may be provided not in the ink supply unit 30 but in the image forming main body 20.

The image forming main body 20 includes: a first sub-tank 21 (ink storage unit), a liquid sending pump 22 (ink supply unit), a second sub-tank 23 (pressure adjustment unit), an ink jet head 24, a return unit 25, and an ink discharge unit 26. A plurality of these ink jet heads are provided for each of the plurality of ink types, each of which is a line head, and receive ink from a common main tank 31 corresponding to the ink type.

The ink supplied from the main tank 31 to the first sub tank 21 of the image forming main body 20 by the supply pump 32 is sent to the inkjet head 24. The ink that is not discharged or leaked from the inkjet head 24 is returned to the first subtank 21 via the return portion 25.

Here, the first sub tank 21 is an ink tank having a smaller capacity than the main tank 31. The first subtank 21 is provided with a first liquid surface sensor 211, and the first liquid surface sensor 211 detects the amount of ink in the first subtank 21 and outputs a detection signal to the control unit 40 (see fig. 4). The first liquid surface sensor 211 may simply detect whether or not the amount of ink is less than a predetermined lower limit reference value, and may output a detection signal to the control unit 40. In addition, the first subtank 21 stores ink returned from the inkjet head 24. The presence or absence of the operation of the supply pump 32 is switched according to the ink detection amount of the first subtank 21, and an appropriate amount of ink is maintained in the first subtank 21.

The liquid feed pump 22 feeds ink from the first subtank 21 to the second subtank 23. The liquid-feeding pump 22 can be a conventionally known one. When the second sub-tank 23 is not in communication with the atmosphere or the air tank 234, the ink pressurized by the liquid-feeding operation of the liquid-feeding pump 22 is supplied to the inkjet head 24 via the second sub-tank 23.

The second subtank 23 is provided with a second liquid level sensor 231, and the second liquid level sensor 231 performs the same operation as the first liquid level sensor 211 of the first subtank 21 with respect to the amount of ink in the second subtank 23.

The second sub-tank 23 communicates with the atmosphere by opening the atmosphere opening valve 232, and communicates with the air tank 234 by opening the atmosphere opening valve 233. When the atmosphere opening valve 233 is opened, the air pressure (negative pressure) in the air tank 234 generates the ink pressure and the pressure difference on the nozzle surface of the inkjet head 24, and the ink pressure is adjusted so that the ink corresponding to the pressure difference is supplied to the inkjet head 24 when the pressure difference changes due to the discharge of the ink or the like, without normally leaking the ink from the nozzles. When the

atmosphere opening valves

232 and 233 are closed, the ink pressurized in accordance with the liquid-feeding operation of the liquid-feeding pump 22 is fed to the inkjet head 24 via the second subtank 23 as described above.

The pressure in the air tank 234 can be appropriately adjusted.

The inkjet head 24 causes ink to flow in from the inlet 241, distributes the ink to individual channels 2471 (see fig. 3) of each of the plurality of nozzles that discharge the ink, and causes undischarged ink to flow out from the

outlets

242 and 243. The inlet 241 is connected to the second subtank 23, and the

outlets

242 and 243 are connected to the first subtank 21 via the reflux unit 25. The recirculation unit 25 is connected between the

outlets

242 and 243 and the first subtank 21 by an ink flow path (recirculation flow path) independently, and a first recirculation valve 251 (first discharge valve) and a second recirculation valve 252 (second discharge valve) are provided in the recirculation flow path, respectively, to switch whether or not ink is circulated (whether or not ink is discharged).

The atmosphere opening valve 233, the first return valve 251, and the second return valve 252 are all solenoid valves that are electromagnetically opened and closed under the control of the control unit 40.

The ink discharge unit 26 receives the ink when the ink is discharged from the nozzle opening of the inkjet head 24 to the outside of the recording medium by a maintenance operation or the like, or when the ink leaks. The ink tray 261 is a receiving tray that receives ink from these nozzles. The waste liquid tank 262 stores the ink received by the ink tray 261. Here, the ink stored in the waste liquid tank 262 is discarded, but may be stored and reused for each ink type. Here, the ink tray 261 is configured such that: the head unit 282 can be moved to a position facing the nozzle opening while increasing the distance from the conveyance surface. Alternatively, the ink tray 261 may be set at a predetermined maintenance position, and the head unit 282 may be moved as necessary to dispose the nozzle surface of the inkjet head 24 at a position facing the ink tray 261.

Fig. 3 is a cross-sectional view of the ink flow path in the inkjet head 24 viewed from the front side.

The plurality of inkjet heads 24 mounted on the head unit 282 are oriented in the front view when viewed from the conveyance direction.

The ink flow path in the inkjet head 24 includes: a common ink chamber 245 (common flow path) to which the inlet 241 and the

outlets

242 and 243 are connected, and an ink discharge portion 247 (head chip) that discharges ink from each nozzle.

The ink flowing from the inlet 241 is transferred to the common ink chamber 245. The filter 246 is provided in the common ink chamber 245, and the inlet 241 communicates with one side (the upstream ink chamber 2451) of the filter 246. The outlet 243 (second discharge port) is provided on the same side as the inlet 241 with respect to the filter 246 (upstream ink chamber 2451), and the outlet 242 (first discharge port) is provided on the opposite side of the inlet 241 with the filter 246 interposed therebetween (downstream ink chamber 2452).

The filter 246 prevents passage of foreign matter within the ink. In addition, the filter 246 suppresses passage of bubbles. Here, in the inkjet recording apparatus 100, the inkjet head 24 is disposed substantially horizontally to the filter 246. Thus, when air bubbles flow in from the inlet 241, the air bubbles are generally close to the top side of the upstream ink chamber 2451 and are difficult to contact the filter 246 or pass through the filter 246. A through hole 2452a communicating with each nozzle of the ink discharge portion 247 is provided in the bottom surface of the downstream ink chamber 2452.

The ink discharge unit 247 includes: a plurality of individual flow paths 2471, and nozzles 2472 corresponding to the individual flow paths 2471, respectively, discharge ink from openings of the nozzles 2472. The individual flow path 2471 is installed so as to match the position of the through hole 2452a of the downstream ink chamber 2452, and thereby ink in the common ink chamber 245 is distributed to the nozzles 2472.

The openings of the plurality of nozzles 2472 are arranged at predetermined intervals (pitches) in the width direction on the nozzle surface of each inkjet head 24. The arrangement of the nozzle openings is not particularly limited, and may be a simple one-dimensional arrangement, or a zigzag arrangement having a plurality of rows in the transport direction. Preferably, the composition is: the nozzle openings provided in the ink jet heads 24 adjacent to each other in the width direction are partially arranged repeatedly in the width direction, and thus ink is reliably discharged over the entire width of the recording medium.

An actuator (not shown), for example, a piezoelectric element, is provided in contact with the wall surface of the individual flow path 2471, and the pressure of the ink in the individual flow path 2471 is changed by the operation (driving operation) of the actuator in accordance with a driving signal output from the head driving unit 54 (see fig. 4), whereby ink droplets are discharged from the opening of the nozzle 2472 at an appropriate liquid amount, droplet shape, and speed.

The drive signal is not particularly limited, and a voltage waveform (discharge waveform) that continuously outputs a trapezoidal waveform on the low voltage side (negative voltage side) and the high voltage side with respect to a reference voltage (ground voltage, etc.) is used. Here, by applying a high voltage, the actuator compresses the individual flow path 2471 (pressure chamber) to increase the ink pressure, and by applying a low voltage, the actuator expands the individual flow path 2471 to decrease the ink pressure. That is, here, the ink pressure is once decreased to introduce the ink to the depth side of the nozzle, and then the ink pressure is increased to be discharged from the nozzle (discharge driving operation). The head driving unit 54 outputs a driving voltage type having a microvibration waveform in which the potential difference (i.e., amplitude) between the high voltage and the low voltage from the reference voltage is smaller than that at the time of ink discharge, thereby reducing pressure fluctuation caused by ink, enabling a microvibration operation in which ink vibrates inside the nozzle without substantially discharging ink from the nozzle, and stirring the ink inside the nozzle when ink is not discharged for a predetermined time or longer to prevent thickening due to evaporation of ink or the like near the nozzle opening.

Fig. 4 is a block diagram showing a functional configuration of the inkjet recording apparatus 100 according to the present embodiment.

As described above, the inkjet recording apparatus 100 includes: the supply pump 32, the supply valve 33, the liquid-sending pump 22, the first liquid level sensor 211, the second liquid level sensor 231, the

atmosphere opening valves

232, 233, the first return valve 251, the second return valve 252, the drum heater 2811, and the like. Further, the inkjet recording apparatus 100 includes: a control unit 40, a unit position adjustment drive unit 58, an ink heater 2822, a conveyance drive unit 52, a cleaner drive unit 53, a head drive unit 54 (drive unit), a tray drive unit 55, an irradiation drive unit 51, an operation display unit 56, a communication unit 57, a bus 59, and the like.

The control unit 40 controls the overall operation of the inkjet recording apparatus 100. The control Unit 40 includes a CPU41(central processing Unit), a RAM42(Random Access Memory), a ROM43(Read Only Memory), a Memory 44, and the like.

The CPU41 performs various arithmetic operations to control the conveyance of the recording medium, the discharge of ink, the maintenance operation, and the like in the inkjet recording apparatus 100. The maintenance action includes: and an air bubble discharge process for discharging the air bubbles in the ink flow path. The CPU41 performs various processes for recording images based on image data, state signals of each unit, clock signals, and the like, in accordance with programs read from the ROM 43.

The RAM42 provides the CPU41 with a memory space for work, and stores temporary data.

The ROM43 stores control programs, initial setting data, and the like. The control program includes the program related to the bubble discharge processing described above. In addition, the ROM43 includes: a nonvolatile memory capable of overwriting updates and the like, and can store setting data and the like that are set and maintained at any time. The memory 44 includes a RAM that temporarily stores image data of a recording target.

The conveyance drive unit 52 generates and outputs drive signals for causing the rotation motor of the image forming drum 281 and the motor for rotating each of the rollers of the sheet feeding plate 12 and the sheet discharge unit 29 to rotate in an appropriate direction and at an appropriate speed. The conveyance drive unit 52 outputs drive signals corresponding to the rotational direction and the rotational speed of each motor based on the control signal from the control unit 40.

The cleaner driving unit 53 operates a wiper, not shown, to wipe off and remove ink and ink mist adhering to the nozzle surface. As the wiper, a roll-up nonwoven fabric, a sponge material, a blade member, or the like can be used depending on the shape, material, and the like of the nozzle surface. Further, the cleaning liquid may be applied to the wiper, or the cleaning liquid may be wiped off by a dry nonwoven fabric or the like after the wiping operation of the nozzle surface or the like is performed using the cleaning liquid.

The head driving unit 54 generates and outputs a driving voltage signal for deforming (driving) the pressure chamber (piezoelectric element) in order to appropriately discharge the ink in the ink discharge unit 247. The head driving unit 54 selects a voltage waveform pattern stored in advance based on a control signal from the control unit 40, generates a drive voltage signal for power amplification, and switches whether or not the drive voltage signal is to be output to each piezoelectric element in accordance with image data input from the memory 44.

The wiring related to the head driving unit 54 is formed in the inkjet head 24 together with the ink flow path, and is formed locally and separately.

The irradiation driving unit 51 applies a predetermined voltage to the L ED of the irradiation unit 283 in accordance with a control signal from the control unit 40, and causes the current to flow, thereby causing the L ED to emit ultraviolet rays.

The unit position adjustment drive unit 58 outputs drive signals to a motor and a brake for position adjustment based on a control signal from the control unit 40, and moves and fixes the head unit 282 to a desired position.

The tray driving section 55 moves the ink tray 261 in accordance with a control signal from the control section 40. As the movement operation of the ink tray 261, various known techniques such as a gear train driven by a motor, an actuator, and the like can be used. In this case, the positional relationship between the ink tray 261 and the head unit 282 (inkjet head 24) does not need to be as strict as in the case of recording an image, and the ink discharged from the inkjet head 24 may not fall off the ink tray 261. Further, as long as the head unit 282 is not separated from the transport surface by a predetermined height or more, as long as the ink tray 261 is not moved to a position facing the inkjet head 24, and/or as long as the ink tray 261 is not retracted, a collision prevention mechanism that does not bring the head unit 282 closer to the transport surface by a predetermined height or less may be provided, and the control unit 40 may perform control so as not to cause collision.

The ink heater 2822 heats and maintains the ink discharged from the head unit 282 to an appropriate temperature, thereby maintaining the viscosity and the like of the ink in an appropriate state. In addition, when ink of a type that gels at room temperature or low temperature is used as the ink, the ink heater 2822 has a structure that heats the ink in the entire ink flow path described above. The temperature of the ink is estimated from a temperature measured by a temperature measuring unit, not shown, in the vicinity of the nozzle of the inkjet head 24, and the operating state of the ink heater 2822 is controlled based on the temperature.

The communication unit 57 is a communication interface for controlling a communication operation with AN external device, and includes, for example, one or more interfaces corresponding to various communication protocols, such as AN L AN port and a L AN card, as the communication interface, the communication unit 57 acquires image data to be recorded and setting data (task data) related to image recording from the external device based on control by the control unit 40, and can transmit status information and the like to the external device.

The operation display unit 56 displays the state of the inkjet recording apparatus 100, operation menus, and the like in accordance with a control signal from the control unit 40, and receives an operation by a user and outputs the operation to the control unit 40. The operation display unit 56 includes, for example: and a liquid crystal display unit in which a touch sensor as an operation receiving means is provided to overlap a display screen as a display means. The control unit 40 performs a control operation of causing the liquid crystal display unit to display a state, various menus for receiving commands from the touch sensor, and the like, and causing each unit of the inkjet recording apparatus 100 to execute processing corresponding to the content and position information of the displayed menus, and the touch operation of the user detected by the touch sensor.

The bus 59 is a path for electrically connecting the above-described respective components to exchange signals.

In addition to these configurations, the inkjet recording apparatus 100 may include a notification operation unit such as an L ED lamp and/or a beep generation unit used for the notification operation, a line sensor for detecting an image quality abnormality (defect) of an image formed on a recording medium, a reading unit such as a placement abnormality detection sensor for detecting that a supplied recording medium is not normally placed on a conveyance surface, and the like.

Next, the bubble discharge operation of the ink jet recording apparatus 100 according to the present embodiment will be described.

The inkjet recording apparatus 100 of the present embodiment performs a bubble discharge process (bubble discharge operation) during ink filling into the ink flow path (refilling) or during maintenance or the like when a predetermined recording failure is detected during image recording. The bubble discharge process may be automatically executed in conjunction with the above-described conditions, but may be started based on a predetermined input operation by the user to the operation display unit 56.

In the bubble discharge process, the ink-jet recording apparatus 100 operates the liquid-feeding pump 22 with the first return valve 251 opened and the second return valve 252 opened as necessary to return the ink in the common ink chamber 245 to the first subtank 21, and discharges the bubbles in the common ink chamber 245 from the common ink chamber 245 to the first subtank 21. At this time, while the ink in the individual flow path 2471 is caused to generate a small pressure fluctuation corresponding to the type of the driving voltage of the micro-vibration waveform, the ink is leaked from the nozzle opening portion in parallel by the ink pressure caused by the liquid-sending operation of the liquid-sending pump 22, and the air bubbles entering the nozzle are discharged from the nozzle opening portion. The ink pressure at this time needs to be a pressure at which ink reliably leaks from all the nozzles, and the ink pressure can be continuously leaked from all the nozzles regardless of the phase of the driving voltage type of the micro-vibration waveform or the like.

Fig. 5 is a flowchart showing the control procedure of the bubble discharge process performed by the inkjet recording apparatus 100 by the control unit 40.

When the bubble discharge processing is started, the control unit 40(CPU41) outputs a control signal to the cell position adjustment drive unit 58 as necessary to increase the distance of the head cells 282 from the conveyance surface, and outputs a control signal to the tray drive unit 55 to cause the ink tray 261 to face the nozzle surface. The control unit 40 closes the atmosphere opening valve 233, and cuts off the second sub-tank 23 from the air tank 234 (step S101).

The control portion 40 opens the first return valve 251 to communicate the downstream ink chamber 2452 with the first subtank 21 (step S102). At this time, the controller 40 may open the second reflux valve 252. The controller 40 operates the liquid feeding pump 22 to feed the ink under pressure, and starts the pressure supply of the ink to the inkjet head 24 through the second subtank 23. The control unit 40 outputs a control signal to the head drive unit 54, and continuously outputs a drive voltage signal for a micro-vibration waveform to the actuator corresponding to each individual flow path 2471 (step S103), and performs a drive operation (micro-drive operation) of the actuator. Although there is no problem even if the start of the supply of ink under pressure and the start of the output of the drive voltage signal are slightly shifted, it is preferable that the supply of ink under pressure and the output of the drive voltage signal are performed substantially simultaneously.

After a predetermined time has elapsed, the control unit 40 stops the operation of the liquid-feeding pump 22 and stops the output of the driving voltage of the micro-vibration waveform (step S104). The control unit 40 closes the first reflux valve 251 (step S105). When the second return valve 252 is opened, the controller 40 closes the second return valve 252 at the same time.

The control unit 40 performs an operation of returning the ink level (meniscus) of the nozzle 2472 as necessary (step S106). The control unit 40 outputs a control signal to the head driving unit 54 to output a discharge waveform, and performs an ink discharge operation from each nozzle.

The control unit 40 retracts the ink tray 261 from the nozzle surface, and opens the atmosphere opening valve 233 of the second subtank 23 (step S107). At this time, the control unit 40 can output a control signal to the cleaner driving unit 53 to perform a cleaning operation of the nozzle surface and the like. Then, the control unit 40 ends the bubble discharge process.

[ modified examples ]

Fig. 6A and 6B are diagrams showing modifications of the inkjet recording apparatus 100 according to the present embodiment.

As shown in fig. 6A, in the recirculation portion 25a, the recirculation passages communicating with the

outlets

242 and 243 may be joined together and connected to the first sub-tank 21 via the first recirculation valve 251. In this case, the flow path resistance of the portion is made sufficiently larger than the flow path resistance of the filter 246 so that the ink does not flow from the outlet 243 to the outlet 242.

As shown in fig. 6B, the outlet 243 for discharging ink from the upstream ink chamber 2451 may not be provided. In this case, the ink must be discharged (or leaked) from the nozzle 2472 or discharged from the outlet 242 after passing through the filter 246.

As described above, the inkjet recording apparatus 100 of the present embodiment includes: an inkjet head 24 provided with nozzles 2472 that discharge ink; a liquid feeding pump 22 for supplying ink to the inkjet head 24; a head driving unit 54 that performs a driving operation for generating pressure fluctuations for discharging ink from the nozzles; and a control unit 40 that controls operations of the liquid-feeding pump 22 and the head drive unit 54, the inkjet head 24 including: a common ink chamber 245 through which ink supplied to the inkjet head 24 flows; a filter 246 provided in the common ink chamber 245 and through which the supplied ink passes; individual flow paths 2471 for feeding the ink passed through the filter 246 from the common ink chamber 245 to the nozzles 2472; and an outlet 242 through which the ink in the common ink chamber 245 having passed through the filter 246 is discharged, and the control unit 40 supplies the ink at the pressure at which the ink leaks from the nozzle 2472 by the liquid sending pump 22 and discharges the ink from the outlet 242 while performing a predetermined driving operation by the head driving unit 54 when performing a bubble discharge operation of the ink in the inkjet head 24.

In this way, in the bubble discharge operation, the liquid feeding operation of the liquid feeding pump 22 simultaneously causes leakage of the ink from the individual flow path 2471 of the nozzle 2472 and the inside of the nozzle 2472 and leakage of the ink from the common ink chamber 245 of the outlet 242, and thus, the bubbles can be easily collectively discharged from each position in the ink flow path of the inkjet head 24 in one operation. In this case, by applying a drive voltage to the actuator in a predetermined drive waveform pattern, air bubbles adhering to the individual flow path 2471, the wall surface in the nozzle 2472, and the like can be effectively peeled off and efficiently and reliably discharged from the nozzle opening.

The inkjet recording apparatus 100 of the present embodiment includes: a first subtank 21 that stores ink supplied to the common ink chamber 245; and a return portion 25 for returning the ink discharged from the outlet 242 to the first subtank 21. Accordingly, most of the ink delivered by the liquid delivery pump 22 for discharging bubbles can be returned to the first subtank 21 and reused, and therefore, the unnecessary amount of ink consumption can be reduced.

Further, the first reflux valve 251 is provided for switching the discharge from the outlet 242, and the control unit 40 closes the first reflux valve 251 when a normal discharge operation for recording an image is performed, and opens the first reflux valve 251 when a bubble discharge operation is performed.

This enables the flow of ink and the ink pressure in the inkjet head 24 to be appropriately controlled and adjusted.

Further, the apparatus comprises: the outlet 243 for discharging ink that has not passed through the common ink chamber 245 of the filter 246, and the control unit 40 causes the supplied ink to be discharged at least from the outlet 242 when the bubble discharge operation is performed.

That is, if necessary, ink, that is, air bubbles and the like can be discharged from the inkjet head 24 without passing through the filter 246, and large air bubbles and the like can be quickly discharged without passing through the filter 246. Whether or not to discharge from the outlet 243 can be appropriately selected.

Further, the apparatus comprises: the second return valve 252 is switched to allow or not to discharge the ink from the outlet 243, and the control unit 40 closes the second return valve 252 at least in the case of a normal discharge operation for recording an image, so that the flow of the ink and the ink pressure in the ink jet head 24 can be appropriately controlled and adjusted.

In the case of performing the bubble discharge operation, the control unit 40 causes the head driving unit 54 to perform a minute driving operation in which a pressure fluctuation that does not cause ink to be discharged from the nozzles 2472 is generated during the image recording operation.

By using the minute drive waveform in this way, the ink is not discharged from the nozzle more than necessary, and the discharge pressure is prevented from rising excessively by further pressurizing the ink pressurized by the operation of the liquid-sending pump 22, whereby the generation of unnecessary mist or the like can be suppressed. Further, by using the same drive waveform as that used in general, it is not necessary to increase the types of drive waveforms to be held and output, and the drive operation can be simplified.

The present invention is not limited to the above embodiment, and various modifications can be made.

For example, in the above-described embodiment, the bubble discharge process is performed by driving the actuator with a driving voltage type based on a normal micro-vibration waveform, but the present invention is not limited thereto. The drive based on the discharge waveform voltage may be performed, or the actuator may be driven at a vibration frequency different from the normal drive waveform, for example, at a drive voltage type having a lower frequency than the output of the normal drive waveform, thereby reducing power consumption.

In the above-described embodiment, the case where the inkjet head 24 is attached so that the filter 246 is substantially horizontal has been described, but the present invention is not limited to this. For example, the filter 246 may also be inclined diagonally in a direction toward the

outlets

242, 243. In this case, the bubbles existing in the upstream ink chamber 2451 and the downstream ink chamber 2452 are easily moved toward the

outlets

242 and 243 by only the buoyancy.

The discharge waveform and the micro-vibration waveform may be not trapezoidal wave shapes but rectangular waves or a combination thereof. In the case of combining vibrations of a plurality of amplitudes and waveforms, the waveform pattern in the case of discharging bubbles may be different from the normal discharge waveform and the micro-vibration waveform.

Further, as the above-described embodiment, a piezoelectric type inkjet recording apparatus that discharges ink and vibrates minutely by using an actuator using a piezoelectric element has been described as an example, but the actuator may be an element other than the piezoelectric element, for example, a magnetostrictive element, and the present invention can be similarly applied to a thermal type inkjet recording apparatus.

In the above embodiment, the ink is leaked to the ink tray 261, but a sponge material absorbing the ink may be used and only the recording medium may be used.

The meniscus recovery operation need not be performed in a set with the bubble discharge process, and may be performed only as needed at the start of normal image recording.

In the above embodiment, the liquid-sending pump 22 can supply the ink to the inkjet head 24 under pressure via the second sub-tank 23, but may have another configuration, and for example, when the ink is sent to the inkjet head 24 under pressure, a flow path bypassing the second sub-tank 23 may be used.

Further, although the one-pass type inkjet recording apparatus including the line head in the above-described embodiment has been described as an example, a scanning type inkjet recording apparatus that discharges ink onto a recording medium while moving an inkjet head or a multi-pass type inkjet recording apparatus may be used.

Further, specific details such as the structure, arrangement, and control operation sequence shown in the above embodiments may be changed as appropriate within a scope not departing from the gist of the present invention.

Industrial applicability of the invention

The present invention can be used in an inkjet recording apparatus.

Description of the reference numerals

A media supply; a paper supply tray; a sheet feed plate; 121. a roller; a belt; a media discharge; a paper discharge tray; an image forming main body portion; a first sub-tank; a first level sensor; a liquid feed pump; a second sub-tank; a second liquid level sensor; 232. an atmospheric opening valve; an air tank; an inkjet head; an inlet; 242. an outlet; 245.. a common ink chamber; 2451. 2452.. a downstream ink chamber; 2452a. A filter; 247.. ink discharge; a separate flow path; a nozzle; 25. a return portion; a first reflux valve; a second backflow valve; an ink discharge portion; an ink tray; a waste liquid tank; an interface unit; a swing arm portion; 272. a cross-over drum; an image forming drum; a drum heater; a head unit; an ink heater; 283.. an irradiation portion; 283a. A sheet discharge portion; 291.. handover rollers; 292. a roller; a belt; an ink supply; a main tank; a filter; a supply pump; a supply valve; a control portion; a CPU; a RAM; ROM; a memory; an irradiation driving section; a delivery drive; 53.. a cleaner drive; a head drive portion; a tray driving portion; 56.. an operation display part; a communication portion; 58.. a unit position adjustment drive; a bus; an inkjet recording apparatus.

Claims

1. An inkjet recording apparatus, comprising:

an inkjet head provided with a nozzle that discharges ink;

an ink supply unit that supplies ink to the inkjet head;

a driving unit that performs a driving operation for generating a pressure variation related to the discharge of the ink in the nozzle; and

the ink jet head includes:

a common flow path through which ink supplied to the inkjet head flows;

individual flow paths for feeding the ink passed through the filter from the common flow path to the nozzles, respectively; and

a first discharge port that discharges ink in the common flow path passing through the filter,

in the case of performing the bubble discharge operation of the ink in the inkjet head, the control unit supplies the ink by the ink supply unit at a pressure at which the ink leaks from the nozzle while performing a predetermined driving operation by the driving unit, and discharges the ink from the first discharge port,

2. The inkjet recording apparatus according to claim 1, comprising:

an ink storage unit that stores the ink supplied to the common flow path; and

3. The inkjet recording apparatus according to claim 1 or 2,

a first discharge valve capable of switching whether or not discharge from the first discharge port is possible,

the controller closes the first discharge valve when a normal discharge operation related to image recording is performed, and opens the first discharge valve when the bubble discharge operation is performed.

4. The inkjet recording apparatus according to claim 1 or 2,

a second discharge port for discharging ink in the common flow path that has not passed through the filter,

5. The inkjet recording apparatus according to claim 4,

the control unit closes the second discharge valve at least when a normal discharge operation related to image recording is performed.